diff --git a/wenet/dataset/processor.py b/wenet/dataset/processor.py
index 4800dcdc8..d6bd1c166 100644
--- a/wenet/dataset/processor.py
+++ b/wenet/dataset/processor.py
@@ -624,7 +624,7 @@ def padding(data):
                                     padding_value=0)
         padding_labels = pad_sequence(sorted_labels,
                                       batch_first=True,
-                                      padding_value=0)
+                                      padding_value=-1)
         padded_wavs = pad_sequence(sorted_wavs,
                                    batch_first=True,
                                    padding_value=0)